A conventional approach to multimode system selection uses only a system preference. As examples, the preference may be for various systems of CDMA and GSM families. However, this conventional system selection approach leads to the problem of the MS attempting to select a preferred (higher priority) system in another network in geographic areas where a system of the home network is present. As a general rule, it may be required that the MS attempt to find the home network and to acquire the home network.
What is needed therefore is a multimode system selection technique that permits different modes of operation to provide a solution to the problem of the MS attempting to register to a non-home network when the home network is available in a given geographic region.
Examples of conventional system selection approaches can be found in commonly assigned U.S. Pat. No. 5,903,832, “Mobile Terminal Having Enhanced System Selection Capability”, by Jorma Seppanen, Juha Vaihoja, Mikko Lietsalmi and Jaacko Vantilla, and in U.S. Pat. No. 6,684,082 B1, “Adaptive System Selection Database”, by Kenneth McClure.
The first referenced U.S. patent describes a mobile station that maintains a single, prioritized list of all available networks (all public, residential, and private networks). Access to the various networks is then based on the user's needs. A first type of access is an automatic access, that requires little or no user involvement. A second type of access is to a user-specified network. A third type of access is to a user-specified service (e.g., data, fax, e-mail, etc.) that is supported by at least one of the networks. The mobile station can search for additional networks, and can also search for additional networks that support only a specified type of service, or for a network that supports a service not supported by networks that are already in the list. All of the networks can be searched at once so that the user can readily make a selection from the single, prioritized network list. The network priorities are user programmable by moving network names up and down in the list using a mobile station user interface, such as the mobile station's keypad. The higher the network name is placed in the list, the higher is the priority of the network.
The second above-referenced commonly assigned U.S. patent describes a method to operate a mobile station that includes storing data into a memory within the mobile station, where the stored data includes at least one system operator code (SOC) having an assigned priority value. Upon the mobile station receiving a system identification (SID) associated with the stored SOC, the method stores the SID into the memory so as to have the same priority value that is assigned to the SOC. When the mobile station subsequently receives a transmission containing the SID and not the SOC, the mobile station accesses the memory to determine the priority value associated with the SID, and then controls the operation of the mobile station based on the determined priority value. Controlling the operation of the mobile station may control at least one of a scanning behavior or a camping behavior of the mobile station.